The present invention relates to a vehicle seat, particularly a motor vehicle seat, having a height adjuster for setting the height of a seat frame of the vehicle seat relative to an understructure connected with the vehicle structure, wherein in the event of a crash, a change in the geometry of the height adjuster activates at least one crash locking device which provides an alternative force transfer between the seat frame and the understructure.
A vehicle seat of the above-described type, which is known from DE 199 53 630, has a motor that is effective between the seat frame and the rocker leg for driving the height adjuster, and the geometry of the height adjuster is reversibly changed in the event of a crash when a threshold force is exceeded in a spring-loaded pin and slot system, with a locking device providing additional force transfer between the seat frame and the vehicle structure. This additional force transfer, for example, discharges the drive of the height adjuster and locks the side of the height adjuster having no drive and located opposite the drive. The activation of the locking device is generally reversible, i.e. the vehicle seat can return to its original position.
An aspect of the present invention is the provision of an improved vehicle seat, with a view to reducing the production costs. In accordance with this aspect, a vehicle seat, particularly a motor vehicle seat, has a height adjuster for setting the height of a seat frame of the vehicle seat relative to an understructure connected with the vehicle structure, wherein in the event of a crash, a change in the geometry of the height adjuster activates at least one crash locking device which provides an alternative force transfer between the seat frame and the understructure, characterized in that the change in the geometry of the height adjuster is substantially irreversible.
Due to the fact that the change in the geometry of the height adjuster is irreversible, the height adjuster can be constructed with simpler, more cost-effective and, for example, deformable elements. In comparison with the known vehicle seat, this will reduce the assembly time and production costs. As soon as the crash locking device is activated and locked, the force is transferred via the height adjuster directly and with optimal evenness. In particular, unlocked areas of the height adjuster, such as the side having no drive, are locked, thereby discharging the drive.
In a preferred arrangement, the geometry of the height adjuster is changed through releasing at least one additional degree of freedom of mobility of the height adjuster which, by reason of its increased movability, will then lock the crash locking device; this in turn will reduce the number of degrees of freedom of mobility, preferably causing the height adjuster to become rigid. The rigid locking of the height adjuster by means of the crash locking device can occur through interlocking surfaces such as toothed elements, or by friction caused, for example, by eccentrically curved friction surfaces, or through a combination of these.
In a preferred, easily manufacturable embodiment, the release of the additional degree of freedom of mobility occurs through a substantially irreversible change of status (e.g. deformation) of at least one connecting element holding together, in a fixedly mounted position, two components of the height adjuster which can normally be rotated relative to one another. In the event of a crash, the two components, following the substantially irreversible change of status of the connecting element, move, thereby locking the crash locking device. In a particularly preferred embodiment, which can be produced in a cost-effective way, the connecting element is in the shape of a pin with a predetermined breaking point, the forces bearing on the pin being shearing forces. Another version could also be to hold the two components together by means of a strong spring defining the threshold load.
In a preferred arrangement, the crash locking device functions in two different load directions, i.e. it is suitable for front-end and rear-end crashes. In order to be able, if necessary, to choose and increase the threshold loads independently, there is preferably a pin with a predetermined breaking point for each load direction. Locking can occur through two independent locking devices, or, in order to reduce the number of components, can occur by means of a locking device that functions in both directions, having, for example, a movable locking element acting jointly with different locking counter-elements according to the load direction. The movable locking element can consist of several components or, to save space, of a monoblock also providing the additional joint for the additional degree of freedom of mobility of the height adjuster.